Antitheft interrupt system for vehicle starter power circuit

ABSTRACT

A vehicle antitheft system includes a housing connectable to the casing of a starter motor and a silicon controlled rectifier (SCR) disposed in the housing. The system includes a battery connector which engages the starter motor power line from the battery, and a starter connector which engages the power terminal of the starter motor, with the SCR being in electrical series between the connectors. A control circuit is mounted in the housing, and the control circuit closes the power switch for a predetermined period upon receipt of an enable signal from a hand-held rf generator. Consequently, the vehicle can be started by turning the ignition switch only during the predetermined period.

This application is a continuation of application Ser. No. 08/577,977,filed Dec. 22, 1995, now U.S. Pat. No. 5,564,376.

FIELD OF THE INVENTION

The present invention relates generally to vehicles, and moreparticularly to override-resistant vehicle antitheft systems.

BACKGROUND

Vehicle antitheft systems have been provided that function by disablinga component in the ignition system of a vehicle unless a security codeis transmitted to the system prior to starting the vehicle. An exampleof such a device is disclosed in U.S. Pat. No. 4,733,638 to Anderson,which discloses a transmitting device that can be manually operated toenergize a relay within the casing of a vehicle starter motor. In turn,the relay, once energized, closes an auxiliary contact that is alsolocated in the casing of the starter motor to thereby complete theelectrical path from the vehicle's battery to a conventional startersolenoid. In accordance with well-known principles, when the ignitionkey is rotated to close the ignition switch, the starter solenoid bothengages the Bendix gear of the starter with the vehicle flywheel, andcloses a conventional starter switch to complete the electrical pathbetween the battery and the starter motor to turn the Bendix gear andflywheel, thereby starting the vehicle.

Accordingly, the Anderson device, like many if not most such antitheftsystems, does not directly control power to a starter motor, but ratherindirectly controls power to the starter motor by controlling power tothe starter solenoid. A principal reason why power to the solenoid iscontrolled is that the electrical current drawn by the solenoid is muchless than the current drawn by the starter motor, thus permitting theuse of relatively small, inexpensive auxiliary contacts by the antitheftsystems.

While somewhat effective, existing antitheft systems have certaindrawbacks. For example, because many of its components are locatedwithin the casing of the starter motor, the Anderson device mentionedabove cannot be easily integrated with existing starter motors. Further,from the above discussion it will be appreciated that the Andersondevice is intended for use with ignition systems wherein the solenoid ishoused with the starter motor. Indeed, the Anderson device cannot beused in conjunction with ignition systems wherein the solenoid is notco-housed with the starter motor.

Unfortunately, antitheft systems which can disable a starter solenoidthat is housed apart from the starter motor are relatively easy todefeat. This is because the solenoid is typically mounted in a locationon the vehicle that relatively easy to access, compared to accessing thestarter motor, and requires the jumpering of a relatively small amountof current, compared to the current that must be jumpered to defeat acircuit element in the main power line to the starter motor. Asaccordingly recognized by the present invention, it would beadvantageous to provide a vehicle antitheft system which can be easilyand quickly mounted in a comparatively inaccessible location, i.e., onthe starter motor casing, which is difficult to defeat by jumpering, andwhich can be used in conjunction with existing stock starter motors.

It is therefore an object of the present invention to provide a vehicleantitheft system that can be used in conjunction with existing startermotors. Another object of the present invention is to provide a vehicleantitheft system that can be easily and quickly mounted on the startermotor casing of a vehicle. Yet another object of the present inventionis to provide a vehicle antitheft system that is relatively difficult todefeat by jumpering. Still another object of the present invention is toprovide a vehicle antitheft system that interrupts power to the startermotor of a vehicle, unless an enable signal is transmitted to thevehicle. Another object of the present invention is to provide a vehicleantitheft system that is easy to use and cost-effective.

SUMMARY OF THE INVENTION

This invention concerns a vehicle antitheft system that is actuated by aportable signal generator, preferably an rf transmitter, and that isconnected to the starter motor of a vehicle for selectively interruptingthe starting current power line between the battery and the startermotor.

The starter motor includes starter motor windings, a casing, and a powerterminal electrically coupled to the starter motor windings. Inaccordance with the present invention, the antitheft system includes ahousing that is connectable to the casing of the starter motor via arigid adapter or by means of mounting the housing on the battery cablein electrical series therewith, near the starter motor. A batteryconnector is configured for engaging the power line, and a starterconnector is configured for engaging the power terminal of the startermotor. A power switch, preferably a solid state device such as a siliconcontrolled rectifier (SCR), is disposed in the housing in electricalseries between the battery connector and starter connector. Per thepresent invention, a control circuit is electrically connected to thepower switch, and the control circuit is responsive to an enable signalto close the power switch upon receipt of the enable signal.

In the preferred embodiment, the antitheft system includes a portableenable signal generator for generating the enable signal. Also, thepreferred control circuit includes a time delay circuit for causing theSCR to open when a predetermined period after receipt of the enablesignal has elapsed. Moreover, the control signal includes an audiblealarm, and the control circuit activates the audible alarm during thepredetermined period.

The vehicle on which the present antitheft system is used includes anignition switch. As intended herein, the preferred control circuitincludes a voltage regulator for maintaining a predetermined constantvoltage to the starter motor windings during the predetermined periodwhen the ignition switch is closed.

In another aspect of the present invention, an antitheft system forcompleting an electrical path between a vehicle battery power line and avehicle starter motor upon receipt of an enable signal includes anenable signal generator for generating the enable signal. Moreover, theantitheft system includes a power switch which is juxtaposed with thestarter motor and which is connected in series between the battery powerline and the starter motor. A control circuit receives the enable signaland closes the power switch in response thereto.

In still another aspect of the present invention, a method is disclosedfor electrically connecting a battery to a power terminal of a startermotor of a motor vehicle. The present method includes disposing a powerswitch and a control circuit for controlling the power switch in ahousing, and mounting the housing in juxtaposition with the startermotor. Both the battery and starter motor are then electricallyconnected to the power switch. An enable signal is transmitted to causethe control circuit to close the power switch.

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the antitheft system of the presentinvention, shown in its intended environment, with portions cut away forclarity;

FIG. 2 is a partially schematic view of the antitheft system of thepresent invention, with portions shown in phantom;

FIG. 3 is an electrical schematic view of the control circuit; and

FIG. 4 is an exploded perspective view of the housing of the presentinvention with mounting adapters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, the intended environment of the presentinvention can be seen. A motor vehicle, generally designated 200,includes an ignition switch 202 that can be closed by means of a key 204to complete the electrical path between a battery 206 and a startermotor 208 and thereby start the engine 210 of the vehicle 200.Specifically, in a conventional ignition system, when the ignitionswitch 202 is closed, a starter solenoid 212 is electrically connectedto the battery 206, energizing the solenoid 212. In turn, the solenoid212 engages a so-called Bendix gear 214 with the flywheel 216 of thevehicle 200. Also, in a conventional ignition system the solenoid 212closes a starter switch 218 (FIG. 2) in a starting current power line220 to complete the electrical circuit between the battery 206 and thestarter motor 208. Thereby, the starter motor 208, which is coupled tothe Bendix gear 214, is caused to rotate the Bendix gear 214 and, hence,the flywheel 216, starting the engine 210.

It will be appreciated that the current flowing through the startingcurrent power line 220 must be relatively high to generate the torquenecessary to turn the flywheel 216. The intention of the presentinvention is to interpose an antitheft system, which is responsive to acoded signal, in the starting current power line 220 between the battery206 and the starter motor 208. Consequently, as the present inventionrecognizes, jumpering of the antitheft system is made difficult in thatrelatively high starting current must be jumpered to do so. Further, theantitheft system of the present invention is physically juxtaposed withthe starter motor 208, which is typically located in a location that isdifficult to access. By "physically juxtaposed" is meant that theantitheft system is mounted on or within a few inches of the startermotor 208. Consequently, physically tampering with the present antitheftsystem is inhibited.

With the above disclosure in mind, in cross-reference to FIGS. 1 and 2an antitheft system, generally designated 10, includes a hollow plasticor metal housing 12 that is mounted on a casing 222 of the starter motor208 by appropriate means. As but one example of how the housing 12 canbe mounted on the starter motor casing 222, a bracket 14 (FIG. 1) issurroundingly engaged with the housing 12 and casing 222 to clamp thehousing 12 against the casing 222. Alternatively, the starting currentpower line 220 can be cut near (i.e., within a few inches of) thestarter motor 208 and the housing 12 connected to and supported by theends of the power line 220 in electrical series therewith.

In yet another alternate embodiment, referring briefly to FIG. 4, anantitheft system, generally designated 300, includes a housing 302. Thesystem 300 shown in FIG. 4 is in all essential respects identical inconfiguration and operation to the system 10 shown in FIGS. 1-3, exceptthat the housing 302 can be juxtaposed with a starter motor casing bymeans of rigid metal mounting adapters 304, 306. More specifically, astarter/solenoid adapter 304 includes an elongate electricallyconductive shank 308 that is in electrical contact with componentswithin the housing 302 in accordance with principles discussed below,and the adapter 304 includes a hollow eye 310 on the end of the shank308 that is opposed to the housing 302. It will readily be appreciatedthat the eye 310 can be fastened to a starter solenoid lug in electricalcontact therewith, both to support the housing 302 and to effectelectrical communication between the starter/solenoid and the componentswithin the housing 302. Likewise, a rigid elongate electricallyconductive battery adapter 306 is in electrical contact with componentswithin the housing 302 in accordance with principles discussed below,and the adapter 306 includes a partially threaded end 312 that isopposed to the housing 302 for establishing a lug onto which a batterycable can be fastened, to further support the homing 302 and to effectelectrical communication between the battery and the components withinthe housing 302. In any case, all of the preferred embodiments includean antitheft system that juxtaposed with a starter motor casing eitherby being mounted directly on the casing or by being closely spaced fromthe casing and held next to the casing by means of rigid adapters or thestarter motor cabling itself immediately next to the starter motor.

Referring back to FIG. 2, the starter motor 208 includes windings 224that are electrically coupled to an externally threaded power terminal226, as indicated by the dashed line 228. The power terminal 226 extendsoutwardly from the casing 222. In accordance with well-known principles,the power terminal 226 establishes a means by which the battery 206 canbe electrically connected to the starter motor 208 to energize thewindings 224, thereby activating the starter motor 208 to turn theBendix gear 212.

FIG. 2, however, shows that instead of connecting the starting currentpower line 220 directly to the power terminal 226 of the starter motor208 as in a conventional ignition system, per the present invention thepower line 220 is connected to an externally threaded terminal 16 of theantitheft system 10 by means of a battery connector 230. As can beappreciated in reference to FIG. 2, the battery connector 230 is heldonto the terminal 16 in electrical contact therewith by a nut 18 that isthreadably engaged with the terminal 16.

In turn, the terminal 16 is electrically connected to a power switch 20that is disposed in the housing 12. Additionally, FIG. 2 shows that thepower switch 20 is electrically connected to a starter connector 22. Ascan be appreciated in reference to FIG. 2, the starter connector 22 isheld onto the power terminal 226 of the starter motor 208 in electricalcontact therewith by a nut 232 that is threadably engaged with the powerterminal 226.

Thus, in accordance with the present invention and as shown in FIG. 2,the power switch 20 is connected in electrical series in the startingcurrent power line between the battery 206 and the starter motor 208.Consequently, in the present invention the staffer motor cannot receivecurrent from the battery 206, even when the starter switch 218 of thevehicle 200 is closed, unless the power switch 20 is also closed.Furthermore, as described below, the power switch 20 closes to completethe electrical circuit between the battery 206 and starter motor 208only when a control circuit 24 in the housing 12 receives an enablesignal from an enable signal generator 26 (FIG. 1).

Advantageously, the enable signal generator 26 is a hand-held (and thusportable) manipulable device which can be conveniently coupled to thekey 204. In the presently preferred embodiment, the generator 26 is aradiofrequency (rf) amplitude modulated (AM) transmitter model no.TX-99K, made by Ming. When appropriately manipulated, the generator 26broadcasts a coded enable signal to the control circuit 24 to close thepower switch 20. If desired, the control circuit 24 can be "trained" toaccept the code of a preexisting rf transmitter that is concurrentlyused for, e.g., remotely opening the door locks of the vehicle 200 as aperson approaches the vehicle 200.

FIG. 3 shows the details of the control circuit 24. As shown, a voltageregulator 28 is connected in parallel with the battery 206. Theregulator 28 includes a twelve volt power output port +V_(o) that isconnected to a control circuit power line L_(p). Also, the regulator 28includes a ground port -V_(o) that is connected to a control circuitground line L_(g) having an isolated ground G1. In accordance with thepresent invention, the regulator 28 maintains a constant voltage in thecontrol circuit 24 while the power switch 20 is closed and the engine210 is cranking during start-up. In the preferred embodiment, thevoltage regulator 28 is a type 4007 12 volt power module made byBurr-Brown.

As shown in FIG. 3, an input capacitor C1 is connected in parallel withthe battery 206 and the input ports of the regulator 28. Also, an outputcapacitor C2 is connected in parallel with the output port +V_(o) andground port -V_(o) of the regulator 28. The preferred values of theresistors and capacitors of the present invention are set forth in Table1 below.

An enable signal receiver 30 is connected to the power line L_(p). Inthe presently preferred embodiment, the receiver 30 is a type RE-99receiver made by Ming. In accordance with the present invention, thereceiver 30 receives the enable signal from the enable signal generator26 (FIG. 1), and in response sends a control signal to a timer 32 via acontrol signal line L_(c).

Preferably, the timer 32 is a chip trigger timer, and more preferably atype 556 dual timer made by, e.g., National Semiconductor. Accordingly,the skilled artisan will recognize that the timer 32 receives arelatively short duration control signal from the receiver 30 andoutputs a relatively longer duration output pulse at first and secondoutput ports T_(out) ¹ and T_(out) ².

As shown in FIG. 3, the timer 32 is connected to the ground line L_(g)via a timer regulator line L_(tr) and a capacitor C3. Additionally, thetimer 32 is connected to a first time delay capacitor C4 as shown, andthe first time delay capacitor C4 is connected to the timer regulatorline L_(tr) via two resistors R1, R2. A second time delay capacitor C5is connected between the timer 32 and ground in parallel with the firsttime delay capacitor C4. Moreover, as shown a ground port GND of thetimer 32 is connected directly to ground, while a power port PWR of thetimer 32 is connected to the power line L_(p). In the preferredembodiment shown, a resistor R3 is connected between the power lineL_(p) and the control signal line L_(c).

As intended by the present invention, the timer 32 in combination withthe time delay capacitors C4, C5 resistors R1, R2 establishes a timedelay circuit that defines a predetermined enable period, during whichperiod the power switch 20 is closed as further disclosed below. In thepreferred embodiment, the predetermined enable period is about oneminute in length. Additionally, the receiver 30 with resistor R3establishes a trigger circuit for triggering the timer 32 to outputvoltages at the output ports T_(out) ¹ and T_(out) ². It is accordinglyto be understood that the output voltages are generated at T_(out) ¹ andT_(out) ² only during the entire enable period.

Continuing with the description of the control circuit 24 shown in FIG.3, the first output port T_(out) ¹ is connected to the base of a type2N2222 alarm transistor Q1 via a resistor R4. In turn, the collector ofthe alarm transistor Q1 is connected to an audible alarm 34. A type1N4001 protect diode D1 is connected in parallel to the alarm 34 asshown. In one presently preferred embodiment, the alarm 34 is apiezoelectric beeper that emits a beeping sound during the predeterminedenable period. As shown, the alarm 34 is connected to the power lineL_(p) via an alarm line L_(a), with the emitter of the alarm transistorQ1 being connected to ground.

FIG. 3 also shows that the second output port T_(out) ² is connected tothe base of a type 2N2222 driver transistor Q2 via a resistor R5. Inturn, the collector of the driver transistor Q2 is connected to the baseof a type 2N2222 power switch transistor Q3 via a resistor R6. As alsoshown, the collector of the driver transistor Q2 is connected to thepower line L_(p) via a resistor R7, and the collector of the powerswitch transistor Q3 is connected to the power line L_(p) as well, witha resistor R8 separating the connections of the transistors Q2, Q3 tothe power line L_(p). The emitters of both the driver transistor Q2 andpower switch transistor Q3 are connected to ground as shown. In thepreferred control circuit shown, an RC circuit including a capacitor C6and resistor R9 is connected between ground and the power line L_(p).

As shown in FIG. 3, the power switch 20 is connected to the power lineL_(p) between the resistor R8 and the RC circuit established by thecapacitor C6 and resistor R9 for controlling the power switch 20. Thepower switch 20 is preferably a solid state power switch, such as afield effect transistor, bipolar transistor, or silicon controllerrectifier (SCR). More preferably, the power switch 20 is an SCR. Asrecognized by the present invention, by making the power switch 20 anSCR, repeated reliable cycling of the power switch 20 is facilitated,notwithstanding the fact that it must pass the relatively high currentin the starting current power line 220.

With the above disclosure in mind, the operation of the antitheft system10 can be appreciated. A person can manipulate the enable signalgenerator 26 (FIG. 1) to generate an enable signal. The enable signalreceiver 30 (FIG. 3) receives the signal and triggers the timer 32 tooutput voltages at its output ports T_(out) ¹ and T_(out) ² for thepredetermined enable period defined by the time delay circuit describedabove.

In response to the output signal at the first output port T_(out) ¹, thealarm transistor Q1 causes the alarm 34 to beep, indicating that theignition system of the vehicle 200 is enabled. Simultaneously, inresponse to the output signal at the second output port T_(out) ², thedriver transistor Q2 and power switch transistor Q3 send a controlsignal to the power switch 20 to cause it to close.

While the power switch 20 is closed during the predetermined period, theignition system of the vehicle 200 is enabled. Consequently, a personcan engage the key 204 with the ignition switch 202 and start the engine210 by turning the key 204. On the other hand, in the absence of anenable signal or after the predetermined period has elapsed,manipulation of the key 204 cannot start the vehicle 200, because theelectrical path between the battery 206 and starter motor 208 isinterrupted by the open power switch 20.

                  TABLE 1                                                         ______________________________________                                        Component    Value (farads/ohms)                                              ______________________________________                                        C1           10 μF                                                         C2           10 μF                                                         C3           47 μF                                                         C4           47 μF                                                         C5           10 μF                                                         C6           .01 μF                                                        R1           1.1 MΩ                                                     R2           180 KΩ                                                     R3            10 KΩ                                                     R4           470 Ω                                                      R5           470 Ω                                                      R6           240 Ω                                                      R7           240 Ω                                                      R8            75 Ω                                                      R9            1 KΩ                                                      ______________________________________                                    

While the particular ANTITHEFT INTERRUPT SYSTEM FOR VEHICLE STARTERPOWER CIRCUIT as herein shown and described in detail is fully capableof attaining the above-described objects of the invention, it is to beunderstood that it is the presently preferred embodiment of the presentinvention and is thus representative of the subject matter which isbroadly contemplated by the present invention, that the scope of thepresent invention fully encompasses other embodiments which may becomeobvious to those skilled in the art, and that the scope of the presentinvention is accordingly to be limited by nothing other than theappended claims.

What is claimed is:
 1. In a vehicle including a battery, a starter motorincluding starter motor windings and a power terminal electricallycoupled to the starter motor windings, an antitheft system, comprising:ahousing; a starter motor power line mechanically coupled to the housingand electrically connected to the starter motor windings; a batterypower line mechanically coupled to the housing and electricallyconnected to the battery, the battery power line and starter motor powerline supporting the housing therebetween; a power switch disposed in thehousing in electrical series between the battery power line and startermotor power line; and a control circuit electrically connected to thepower switch and responsive to an enable signal to close the powerswitch upon receipt of the enable signal, wherein the control circuitincludes:a time delay circuit for causing the power switch to open whena predetermined period after receipt of the enable signal has elapsed;and an audible alarm, the control circuit activating the audible alarmduring at least a portion of the predetermined period.
 2. The antitheftsystem of claim 1, wherein the power switch is a solid state switch. 3.The antitheft system of claim 2, wherein the solid state switch is asilicon controlled rectifier (SCR).
 4. The system of claim 3, furthercomprising a portable enable signal generator for generating the enablesignal.
 5. The system of claim 1, wherein the vehicle includes anignition switch, and the control circuit further includes a voltageregulator for maintaining a predetermined constant voltage in thecontrol circuit during the predetermined period when the ignition switchis closed.
 6. The system of claim 1, further comprising respective rigidelectrically conductive adapters for mechanically coupling the startermotor power line and battery power line to the control circuit.
 7. Thesystem of claim 1, in combination with the vehicle.
 8. An antitheftsystem for completing an electrical path between a vehicle battery powerline and a vehicle starter motor upon receipt of an enable signal,comprising:an enable signal generator for generating the enable signal;a power switch in series between the battery power line and the startermotor and at least partially supported by the battery power line; and acontrol circuit for receiving the enable signal and closing the powerswitch in response thereto, the control circuit includinga time delaycircuit for opening the power switch when a predetermined period afterreceipt of the enable signal has elapsed; and a voltage regulator formaintaining a predetermined constant voltage in the control circuit. 9.The system of claim 8, further comprising a housing for holding thepower switch and the control circuit.
 10. The system of claim 9, whereinthe starter motor includes windings and a power terminal electricallycoupled to the windings, and the system further includes:a batteryconnector configured for engaging the power line; and a starterconnector configured for engaging the power terminal, wherein the powerswitch is connected in electrical series between the connectors.
 11. Thesystem of claim 10, wherein the power switch is a silicon controlledrectifier (SCR).
 12. The system of claim 8, in combination with avehicle.
 13. In a vehicle including a battery, a starter motor includingwindings, a starter motor power line for electrically connecting thebattery to the starter motor windings, an antitheft system, comprising:ahousing; a starter motor power line mechanically coupled to the housingand electrically connected to the starter motor windings; a batterypower line mechanically coupled to the housing and electricallyconnected to the battery, the battery power line and starter motor powerline supporting the housing therebetween; a power switch disposed in thehousing in electrical series between the battery power line and startermotor power line; and a control circuit electrically connected to thepower switch and responsive to an enable signal to close the powerswitch upon receipt of the enable signal.
 14. In a vehicle including abattery, a starter motor including windings, a starter motor power linefor electrically connecting the battery to the starter motor windings,an antitheft system, comprising:a power switch; a housing for holdingthe power switch; a starter motor power line electrically connected tothe starter motor windings; a first rigid connector electricallyconnecting the starter motor power line to the power switch andmechanically coupling the starter motor power line to the housing; abattery power line electrically connected to the battery; a second rigidconnector electrically connecting the battery power line to the powerswitch and mechanically coupling the battery power line to the housing,such that the housing is supported only by the power lines; and acontrol circuit electrically connected to the power switch andresponsive to an enable signal to close the power switch upon receipt ofthe enable signal.
 15. The system of claim 14, wherein the controlcircuit comprises:a time delay circuit for causing the power switch toopen when a predetermined period after receipt of the enable signal haselapsed; and an audible alarm, the control circuit activating theaudible alarm during at least a portion of the predetermined period. 16.The system of claim 14, wherein the control circuit closes the powerswitch for a time period upon receipt of the enable signal, and thecontrol circuit includes:a voltage regulator for maintaining a constantpredetermined voltage to the control circuit during at least a portionof the time period.
 17. The system of claim 16, wherein the controlcircuit further comprises:a time delay circuit for causing the powerswitch to open when a predetermined period after receipt of the enablesignal has elapsed; and an audible alarm, the control circuit activatingthe audible alarm during at least a portion of the predetermined period.